Primary exercises
- Manually created factor.
In a study participants were asked whether their sport activity is none, oncePerWeek, severalPerWeek or daily.
Build a proper factor for the responses below and store it in a variable w.
Print the factor.
Write the code to count the numbers of occurrences of each level and print the counts.
severalPerWeek, none, none, oncePerWeek, oncePerWeek, oncePerWeek, oncePerWeek, ?, none, none
v <- c( "severalPerWeek", "none", "none", "oncePerWeek", "oncePerWeek", "oncePerWeek", "oncePerWeek", NA, "none", "none" )
w <- factor( v, levels = c( "none", "oncePerWeek", "severalPerWeek", "daily" ) )
w
[1] severalPerWeek none none oncePerWeek oncePerWeek oncePerWeek
[7] oncePerWeek <NA> none none
Levels: none oncePerWeek severalPerWeek daily
fct_count( w )
# A tibble: 5 x 2
f n
<fct> <int>
1 none 4
2 oncePerWeek 4
3 severalPerWeek 1
4 daily 0
5 <NA> 1
- A factor with a random content.
Read help about the function sample.
Then study and try the following lines of code to understand the results.
Next, understand why an error is generated and use replace argument to generate a vector with 100 samples.
Store this vector in a variable v and build a factor w from it.
Finally, count the numbers of occurrences of each level in w.
Ensure, that levels are in order provided in the variable lvl.
lvs <- c( "none", "oncePerWeek", "severalPerWeek", "daily" )
sample( lvs, 3 )
[1] "oncePerWeek" "none" "daily"
sample( lvs, 3 )
[1] "oncePerWeek" "severalPerWeek" "daily"
sample( lvs, 3 )
[1] "daily" "severalPerWeek" "none"
sample( lvs, 100 )
Error in sample.int(length(x), size, replace, prob): cannot take a sample larger than the population when 'replace = FALSE'
v <- sample( lvs, 100, replace = TRUE )
w <- factor( v, levels = lvs )
w
[1] daily none oncePerWeek oncePerWeek oncePerWeek oncePerWeek
[7] daily daily severalPerWeek none daily severalPerWeek
[13] none daily severalPerWeek severalPerWeek none none
[19] severalPerWeek severalPerWeek daily none none oncePerWeek
[25] oncePerWeek daily severalPerWeek severalPerWeek daily oncePerWeek
[31] oncePerWeek none severalPerWeek oncePerWeek severalPerWeek daily
[37] none daily oncePerWeek daily daily severalPerWeek
[43] oncePerWeek oncePerWeek daily none severalPerWeek daily
[49] oncePerWeek severalPerWeek none oncePerWeek daily daily
[55] severalPerWeek daily oncePerWeek oncePerWeek severalPerWeek none
[61] severalPerWeek severalPerWeek severalPerWeek oncePerWeek severalPerWeek daily
[67] severalPerWeek severalPerWeek severalPerWeek severalPerWeek daily none
[73] severalPerWeek oncePerWeek severalPerWeek none none oncePerWeek
[79] oncePerWeek oncePerWeek severalPerWeek none daily daily
[85] oncePerWeek oncePerWeek oncePerWeek none oncePerWeek daily
[91] none oncePerWeek severalPerWeek daily severalPerWeek daily
[97] none oncePerWeek none oncePerWeek
Levels: none oncePerWeek severalPerWeek daily
fct_count( w )
# A tibble: 4 x 2
f n
<fct> <int>
1 none 20
2 oncePerWeek 28
3 severalPerWeek 28
4 daily 24
- Reordering factor levels.
When a factor is shown on an axis of a plot, the order is given by its levels.
The factor w from the previous exercise will be then shown in this order: none, oncePerWeek, severalPerWeek, daily.
But for a picture in a manuscript the following order might be needed: daily, severalPerWeek, oncePerWeek, none.
Apply to w one of the fct_ functions from the tidyverse library to produce a factor w2 with the requested order.
Show the levels of w2.
Again show the number of elements of each level in w2 and compare it with the table of the previous exercise.
w2 <- fct_relevel( w, c( "daily", "severalPerWeek", "oncePerWeek", "none" ) )
levels( w2 )
[1] "daily" "severalPerWeek" "oncePerWeek" "none"
fct_count( w2 )
# A tibble: 4 x 2
f n
<fct> <int>
1 daily 24
2 severalPerWeek 28
3 oncePerWeek 28
4 none 20